<template>
    <div class="ba">
        <ul class="bg-bubbles">
            <li v-for="(item, index) in bubbles" :key="index"></li>
        </ul>
    </div>
</template>
<script>
export default {
    data(){
        return{
            bubbles:[]
        }
    },
    created() {
        this.bubbles.length = 10;
 },
}
</script>
<style lang="less">

.bg-bubbles {
    position: absolute;
    // 使气泡背景充满整个屏幕
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    li {
      position: absolute;
      // bottom 的设置是为了营造出气泡从页面底部冒出的效果；
      bottom: -160px;
      // 默认的气泡大小；
      width: 40px;
      height: 40px;
      background-color: rgba(255, 255, 255, 0.15);
      list-style: none;
      // 使用自定义动画使气泡渐现、上升和翻滚；
      animation: square 15s infinite;
      transition-timing-function: linear;
      // 分别设置每个气泡不同的位置、大小、透明度和速度，以显得有层次感；
      &:nth-child(1) {
        left: 10%;
      }
      &:nth-child(2) {
        left: 20%;
        width: 90px;
        height: 90px;
        animation-delay: 2s;
        animation-duration: 7s;
      }
      &:nth-child(3) {
        left: 25%;
        animation-delay: 4s;
      }
      &:nth-child(4) {
        left: 40%;
        width: 60px;
        height: 60px;
        animation-duration: 8s;
        background-color: rgba(255, 255, 255, 0.3);
      }
      &:nth-child(5) {
        left: 70%;
      }
      &:nth-child(6) {
        left: 80%;
        width: 120px;
        height: 120px;
        animation-delay: 3s;
        background-color: rgba(255, 255, 255, 0.2);
      }
      &:nth-child(7) {
        left: 32%;
        width: 160px;
        height: 160px;
        animation-delay: 2s;
      }
      &:nth-child(8) {
        left: 55%;
        width: 20px;
        height: 20px;
        animation-delay: 4s;
        animation-duration: 15s;
      }
      &:nth-child(9) {
        left: 25%;
        width: 10px;
        height: 10px;
        animation-delay: 2s;
        animation-duration: 12s;
        background-color: rgba(255, 255, 255, 0.3);
      }
      &:nth-child(10) {
        left: 85%;
        width: 160px;
        height: 160px;
        animation-delay: 5s;
      }
    }
    // 自定义 square 动画；
    @keyframes square {
      0% {
        opacity: 0.5;
        transform: translateY(0px) rotate(45deg);
      }
      25% {
        opacity: 0.75;
        transform: translateY(-400px) rotate(90deg)
      }
      50% {
        opacity: 1;
        transform: translateY(-600px) rotate(135deg);
      }
      100% {
        opacity: 0;
        transform: translateY(-1000px) rotate(180deg);
      }
    }
  }
</style>